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- Thermal and environmental simulation of buildingsPublication . Ramos, João António Esteves; Pitarma, Rui A.; Carvalho, Maria da GraçaThe purpose of most buildings is to provide a comfortable and healthy indoor environment for the occupants. As a result of increasing energy prices in the last decades, much effort has been done to reduce the cost arising from mechanical and natural ventilation of buildings. This often involves lowering the outdoor air intake. At the same time, many new pollution sources have been introduced in the buildings. These issues are important if we take into consideration that today the majority of the people spends more than 90% of their time indoors. In this work will be presented a physical and mathematical models to study the three-dimensional turbulent air flow patterns with thermal buoyant effects, the heat transfer, including radiation between walls, the gas contaminant trasnport and the most air transport into mechanical or natural ventilated spaces. the calculations made use of a numerical procedure, which solves the three-dimensional equations for the conservation of mass, momentum, thermal energy and air contaminant transport. The turbulence is modelled by the k-e model and thermal radiation by the discrete transfer method. To validate the mathematical model, the predictions results were compared with experimental data for two different scales - full scale office room and 1/4 laboratory scale model. A physical modelling technique, based on dimensional analysis, was used to derive the physical properties of the laboratory model, designed to provide similarity with the room. The simulation of the air contaminant distribution, the thermal and the air flow patterns in an office natural ventilated room (prototype and model) was performed.
- Dynamic analysis of a refrigerated roomPublication . Carvalho, Maria da Graça; Pitarma, Rui A.; Pereira, Filipe D.; Ramos, João António EstevesThe prediction of velocity and temperature distributions in a refrigerated room generally requires the simultaneous three-dimensional solution of the equations governing the flow pattern (Navier-stokes equations for buoyant flows) and the energy equation. This paper presents numerical predictions and experimental validation of the three-dimensional turbulent flow inside two different three-dimensional refrigeration chambers with forced convection. The refrigerated rooms are a 26 m3 living produce storage room and a 10 m3 yogurt truck refrigerated chamber. Agreement between measured and predicted values was very satisfactory for engineering purposes. The model is very useful in chamber's design since an important tool to predict food storage in order to allow energy savings.
- Three-dimensional natural convection in rooms connected to the outside through large openingsPublication . Ramos, João António Esteves; Martinho, Nuno A. G.; Pitarma, Rui A.; Carvalho, Maria da GraçaThe growing interest in the study of natural convection in geometrically complex enclosures with restricted communication has been stimulated by applications involving energy-efficient passive-solar buildings, natural convection cooling of electronic equipment and room heating and ventilation. Airflow through doorways, windows and other large openings are significant ways in which air, pollutants and thermal energy are transferred from one zone of a building to another or to outside. The present paper describes a numerical method for analysing three-dimensional natural convection in rooms connected to the outside through large openings. The calculations made use of a Computational Fluid Dynamics (CDF) procedure taking into account the effects of buoyancy, heat sources, thermal radiation heat transfer and air flow turbulence. The CDF predictions agree with the experimentally observed features of the flow field, including the vertical air temperature stratification, with a reasonable degree of accuracy.
- The role of computational fluid dynamics in the building energy and environmental analysisPublication . Carvalho, Maria da Graça; Ramos, João António EstevesThe goal of this paper is to introduce a Computational Fluid Dynamics model to study the steady three-dimensional turbulent airflow pattern, with thermal buoyant effects, the heat transfer, the gas contaminant transport and the moist air transport into mechanical or natural ventilated spaces, with furniture and people. The calculations made use of a numerical procedure with solves the three-dimensional steady state equations for the conservation of mass, momentum, thermal energy and air contaminant transport, tanking account of the effects of buoyancy and airflow turbulence. In order to demonstrate its applicability, the code has been used to predict the thermal, the airflow pattern and the environment in an office ventilated room. Based on this predictions and on thermal comfort models it was possible to evaluate the thermal comfort.
- O papel da modelação matemática na optimização da climatização de edifíciosPublication . Ramos, João António Esteves; Pitarma, Rui A.; Martinho, Nuno A. G.; Carvalho, Maria da GraçaA crescente necessidade da utilização de meios de cálculo que permitam a previsão e a visualização das características dos escoamentos do ar, da distribuição da temperatura, da distribuição da humidade do ar e do transporte de contaminantes, em espaços de edifícios ventilados, tem incentivado a investigação na modelação física e matemática desses fenómenos, nessas geometrias complexas. Nesta comunicação, apresenta-se uma "ferramenta" de cálculo que permite modelar os fenómenos tridimensionais associados à circulação turbulenta do ar, à transmissão de calor e à transmissão do vapor de água no ar (humidade). O modelo de simulação computacional desenvolvido foi validado para a caracterização do ambiente interior em edifícios nas suas variantes termo-higrométricas, qualidade do ar e conforto térmico. Nesta comunicação apresentam-se previsões do campo da velocidade, da temperatura do ar e da concentração de vapor de água numa sala de escritório com obstáculos e com fontes interiores de calor e de água. Este tipo de avaliação é fundamental para, em cada caso, conhecer, de uma forma detalhada, a influência dos vários parâmetros do ambiente interior nos ocupantes dos edifícios, quer do ponto de vista do conforto térmico, quer da qualidade do ar.
- Modelação do conforto térmico em salas climatizadasPublication . Ramos, João António Esteves; Pitarma, Rui A.; Carvalho, Maria da GraçaThe goal of this lecture is to introduce a new tool to predict the three-dimensional turbulent air flow pattern and the heat transfer in ventilated buildings